Soil erosion can result in the redistribution of substantial quantities of organic matter within a watershed. A study of sediment dynamics in the Yellow River basin, China, suggests that much of the soil organic carbon dislodged by erosion is buried within the river itself.
Xi Xi Lu of the National University of Singapore and colleagues assessed the effect of soil erosion on sediment and organic carbon fluxes in the Yellow River basin between 1950 and 2010. Using records of soil erosion, together with data on sediment loading and soil and sediment organic carbon content, they estimate that over 130 Gt of soil, which comprised over 1 Gt of organic carbon, was eroded over this period. Of the organic carbon released, around 50% was buried in the river system, much of it behind dams, and around 23% was delivered to the Bohai Sea. The researchers suggest that the rest was broken down during erosion and transport processes, and subsequently released to the atmosphere.
Less carbon would have been captured within the river basin, and more delivered to the ocean or lost to the atmosphere, were it not for the construction of dams and the implementation of soil control measures, such as the conversion of hillslopes into terraces.